Wind energy is one of the available forms of natural energy that can be converted into electrical energy, and is more environmentally friendly compared with generating electrical energy from fossil-fuel such as petroleum or coal. The shape, outline and number of vanes of a wind turbine machine may affect the effectiveness of conversion from wind energy to electrical energy.
Referring to FIG. 1, a conventional anemometer is shown and includes an upright prop 91, three connection rods 92 rotatably mounted on a top of the upright prop 91, and three cup members 93 respectively connected to the connection rods 92. Each of the cup members 93 has a concave inner surface 931 and a convex outer surface 932 that is opposite to the inner surface 931. When wind flows toward the inner surface 931 of one of the cup members 93, since air flowing over the outer surface 932 has a longer path than that of air flowing over the inner surface 931, difference in wind pressure would result therebetween. The difference in wind pressure propels the cup members 93 to rotate.
However, to convert wind power or water power into sufficient electrical power by adopting the structure of the conventional anemometer as an actuator for a power generator, each of the cup members 93 has to be increased in size. Based on Bernoulli's principle, the wind that passes over the enlarged outer surface 931 must have a relatively high speed for successfully propelling the cup members 93. As a result, use of the structure of the conventional anemometer is limited to locations having strong wind flow or water flow.